U.S. patent application number 10/215929 was filed with the patent office on 2003-02-27 for safety systems for power equipment.
Invention is credited to Betts-LaCroix, Jonathan N., Chamberlain, Robert L., D'Ascenzo, David S., Fanning, David A., Fulmer, J. David, Gass, Stephen F., Jensen, Joel F., Johnston, Andrew L., Kim, Sung H., McDonald, Anwyl M., Schramm, Benjamin B..
Application Number | 20030037651 10/215929 |
Document ID | / |
Family ID | 26910503 |
Filed Date | 2003-02-27 |
United States Patent
Application |
20030037651 |
Kind Code |
A1 |
Gass, Stephen F. ; et
al. |
February 27, 2003 |
Safety systems for power equipment
Abstract
A saw with a safety system is disclosed. The safety system
includes a detection system adapted to detect contact between a
person and a blade while the blade is moving. The safety system
further includes a brake system adapted to engage the blade and to
stop the blade when the detection system detects contact between
the person and the blade.
Inventors: |
Gass, Stephen F.;
(Wilsonville, OR) ; Fanning, David A.; (Vancouver,
WA) ; Fulmer, J. David; (Tualatin, OR) ;
D'Ascenzo, David S.; (Portland, OR) ; Betts-LaCroix,
Jonathan N.; (Chatsworth, CA) ; Chamberlain, Robert
L.; (Raleigh, NC) ; Jensen, Joel F.; (Redwood
City, CA) ; Johnston, Andrew L.; (Redwood City,
CA) ; Kim, Sung H.; (Palo Alto, CA) ;
McDonald, Anwyl M.; (Palo Alto, CA) ; Schramm,
Benjamin B.; (Los Gatos, CA) |
Correspondence
Address: |
SD3, LLC
22409 S.W. NEWLAND ROAD
WILSONVILLE
OR
97070
US
|
Family ID: |
26910503 |
Appl. No.: |
10/215929 |
Filed: |
August 9, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60312141 |
Aug 13, 2001 |
|
|
|
Current U.S.
Class: |
83/62.1 ;
83/477.2; 83/DIG.1 |
Current CPC
Class: |
B27B 13/14 20130101;
F16P 3/12 20130101; Y10T 83/7705 20150401; Y10T 83/081 20150401;
Y10T 83/7726 20150401; Y10T 83/7697 20150401; Y10T 83/773 20150401;
Y10T 83/04 20150401; Y10T 83/8773 20150401; Y10S 83/01 20130101;
B27B 5/38 20130101; B23D 59/001 20130101; Y10T 83/778 20150401;
Y10T 83/089 20150401; Y10T 83/141 20150401; B27G 19/02 20130101;
Y10T 83/7788 20150401 |
Class at
Publication: |
83/62.1 ;
83/DIG.001; 83/477.2 |
International
Class: |
B26D 001/14; B27B
013/00 |
Claims
1. A saw comprising: a blade configured to move to cut a work
piece, where the blade includes at least one cutting edge; a motor
adapted to move the blade; a detection system adapted to detect
contact between a person and the blade while the blade is moving;
and a brake system adapted to engage the cutting edge of the blade
and to stop the blade when the detection system detects contact
between the person and the blade.
2. The saw of claim 1, further comprising a frame supporting the
blade, and where the blade is electrically isolated from the
frame.
3. The saw of claim 2 where the detection system is adapted to
capacitively impart an electric signal on the blade and to detect
the occurrence of a determined change in the signal.
4. The saw of claim 1, where the brake system includes a brake pawl
biased to engage the blade.
5. The saw of claim 4, where the brake system includes a spring
configured to move the brake pawl into the blade.
6. The saw of claim 5, where the brake system includes a release
mechanism adapted to selectively restrain the brake pawl from
engaging the blade until the detection system detects contact
between the person and the blade.
7. The saw of claim 6, where the release mechanism includes a fuse
wire that is melted upon detection of contact between the person
and the blade.
8. The saw of claim 1, where at least a portion of the brake system
is housed in a replaceable cartridge.
9. The saw of claim 1, where the detection system is capacitively
coupled to the blade.
10. The saw of claim 9, where the capacitive coupling between the
detection system and the blade includes a drive electrode and a
sense electrode.
11. The saw of claim 1, further including a control system adapted
to monitor the detection system and control actuation of the brake
system.
12. The saw of claim 11, where the control system is adapted to
shut off the motor when contact between a person and the blade is
detected.
13. The saw of claim 11, where the control system is adapted to
test at least part of the brake system to verify that at least part
of the brake system is operational.
14. The saw of claim 1, where the machine is a table saw.
15. The saw of claim 1, where the machine is a miter saw.
16. The saw of claim 1, where the machine is a radial arm saw.
17. The saw of claim 1, where the machine is a circular saw.
18. The saw of claim 1, where the machine is a band saw.
19. A saw comprising: an electrically conductive cutter; detection
means for detecting contact between a person and the cutter, where
the detection system is adapted to capacitively impart an electric
signal on the cutter, and to detect the occurrence of a determined
change in the electric signal on the cutter; and a reaction system
associated with the detection means and the cutter, where the
reaction system is adapted to cause a predetermined action to take
place relative to the cutter upon detection of contact between the
person and the cutter by the detection means.
20. A saw comprising: a blade configured to move to cut a work
piece, where the blade includes at least one cutting edge; a motor
adapted to move the blade; detection means for detecting contact
between a person and the blade; and brake means for stopping the
blade when the detection means detects contact between the person
and the blade.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of and priority from the
following U.S. Provisional Patent Application, the disclosure of
which is herein incorporated by reference: Serial No. 60/312,141,
filed Aug. 13, 2001.
BACKGROUND
[0002] Beginning with the industrial revolution and continuing to
the present, mechanized equipment has allowed workers to produce
goods with greater speed and less effort than possible with
manually-powered tools. Unfortunately, the power and high operating
speeds of mechanized equipment creates a risk for those operating
such machinery. Each year thousands of people are maimed or killed
by accidents involving power equipment.
[0003] As might be expected, many systems have been developed to
minimize the risk of injury when using power equipment. Probably
the most common safety feature is a guard that physically blocks an
operator from making contact with dangerous components of
machinery, such as belts, shafts or blades. In many cases, guards
are effective to reduce the risk of injury, however, there are many
instances where the nature of the operations to be performed
precludes using a guard that completely blocks access to hazardous
machine parts.
[0004] Various systems have been proposed to prevent accidental
injury where guards cannot effectively be employed. For instance,
U.S. Pat. Nos. 941,726, 2,978,084, 3,011,610, 3,047,116, 4,195,722
and 4,321,841, the disclosures of which are incorporated herein by
reference, all disclose safety systems for use with power presses.
These systems utilize cables attached to the wrists of the operator
that either pull back a user's hands from the work zone upon
operation or prevent operation until the user's hands are outside
the danger zone. U.S. Pat. Nos. 3,953,770, 4,075,961, 4,470,046,
4,532,501 and 5,212,621, the disclosures of which are incorporated
herein by reference, disclose radio-frequency safety systems which
utilize radio-frequency signals to detect the presence of a user's
hand in a dangerous area of the machine and thereupon prevent or
interrupt operation of the machine.
[0005] U.S. Pat. Nos. 4,959,909, 5,025,175, 5,122,091, 5,198,702,
5,201,684, 5,272,946, and 5,510,685 disclose safety systems for use
with meat-skinning equipment, and are incorporated herein by
reference. These systems interrupt or reverse power to the motor,
or disengage a clutch, upon contact with a user's hand by any
dangerous portion of the machine. Typically, contact between the
user and the machine is detected by monitoring for electrical
contact between a fine wire mesh in a glove worn by the user and
some metal component in the dangerous area of the machine. Although
such systems are suitable for use with meat skinning machines, they
are relatively slow to stop the motion of the cutting element
because they rely on the operation of solenoids or must overcome
the inertia of the motor. However, because these systems operate at
relatively low speeds, the blade does not need to be stopped
rapidly to prevent serious injury to the user.
[0006] U.S. Pat. Nos. 3,785,230 and 4,026,177, the disclosures of
which are herein incorporated by reference, disclose a safety
system for use on circular saws to stop the blade when a user's
hand approaches the blade. The system uses the blade as an antenna
in an electromagnetic proximity detector to detect the approach of
a user's hand prior to actual contact with the blade. Upon
detection of a user's hand, the system engages a brake using a
standard solenoid. Unfortunately, such a system is prone to false
triggers and is relatively slow acting because of the solenoid.
U.S. Pat. No. 4,117,752, which is herein incorporated by reference,
discloses a similar braking system for use with a band saw, where
the brake is triggered by actual contact between the user's hand
and the blade. However, the system described for detecting blade
contact does not appear to be functional to accurately and reliably
detect contact. Furthermore, the system relies on standard
electromagnetic brakes operating off of line voltage to stop the
blade and pulleys of the band saw. It is believed that such brakes
would take 50 ms-1 s to stop the blade. Therefore, the system is
too slow to stop the blade quickly enough to avoid serious
injury.
[0007] None of these existing systems have operated with sufficient
speed and/or reliability to prevent serious injury with many types
of commonly used power tools. Although proximity-type sensors can
be used with some equipment to increase the time available to stop
the moving pieces, in many cases the user's hands must be brought
into relatively close proximity to the cutting element in the
normal course of operation. For example, many types of woodworking
equipment require that the user's hands pass relatively close to
the cutting tools. As a result, existing proximity-type sensors,
which are relatively imprecise, have not proven effective with this
type of equipment. Even where proximity sensors are practical,
existing brake systems have not operated quickly enough to prevent
serious injury in many cases.
[0008] In equipment where proximity-type detection have not proven
effective, the cutting tool must stop very quickly in the event of
user contact to avoid serious injury. By way of example, a user may
feed a piece of wood through a table saw at a rate of approximately
one foot per second. Assuming an average reaction time of
approximately one-tenth of a second, the hand may have moved well
over an inch before the user even detects the contact. This
distance is more than sufficient to result in the loss of several
digits, severing of vital vessels and tendons, or even complete
severing of a hand. If a brake is triggered immediately upon
contact with the saw's blade, the blade must be stopped within
approximately one-hundredth of a second to limit the depth of
injury to one-eighth of an inch. Standard solenoids or other
electromagnetic devices are generally not designed to act in this
time scale, particularly where significant force must be generated.
For instance, in the case of solenoids or electromagnetic brakes
that operate on 60 hz electrical power, it is possible that the
power line will be at a phase that has low voltage at the time the
brake is triggered and several milliseconds may elapse before the
voltage reaches a sufficient level even to begin physical
displacement of the brake, much less achieve a complete stoppage of
the blade or cutting tool.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic block diagram of a machine with a
fast-acting safety system according to the present invention.
[0010] FIG. 2 is a schematic diagram of an exemplary safety system
in the context of a machine having a circular blade.
DETAILED DESCRIPTION
[0011] A machine according to the present invention is shown
schematically in FIG. 1 and indicated generally at 10. Machine 10
may be any of a variety of different machines adapted for cutting
workpieces, such as wood, including a table saw, miter saw (chop
saw), radial arm saw, circular saw, band saw, jointer, planer, etc.
Machine 10 includes an operative structure 12 having a cutting tool
14 and a motor assembly 16 adapted to drive the cutting tool.
Machine 10 also includes a safety system 18 configured to minimize
the potential of a serious injury to a person using machine 10.
Safety system 18 is adapted to detect the occurrence of one or more
dangerous conditions during use of machine 10. If such a dangerous
condition is detected, safety system 18 is adapted to engage
operative structure 12 to limit any injury to the user caused by
the dangerous condition.
[0012] Machine 10 also includes a suitable power source 20 to
provide power to operative structure 12 and safety system 18. Power
source 20 may be an external power source such as line current, or
an internal power source such as a battery. Alternatively, power
source 20 may include a combination of both external and internal
power sources. Furthermore, power source 20 may include two or more
separate power sources, each adapted to power different portions of
machine 10.
[0013] It will be appreciated that operative structure 12 may take
any one of many different forms, depending on the type of machine
10. For example, operative structure 12 may include a stationary
housing configured to support motor assembly 16 in driving
engagement with cutting tool 14. Alternatively, operative structure
12 may include a movable structure configured to carry cutting tool
14 between multiple operating positions. As a further alternative,
operative structure 12 may include one or more transport mechanisms
adapted to convey a workpiece toward and/or away from cutting tool
14.
[0014] Motor assembly 16 includes one or more motors adapted to
drive cutting tool 14. The motors may be either directly or
indirectly coupled to the cutting tool, and may also be adapted to
drive workpiece transport mechanisms. Cutting tool 14 typically
includes one or more blades or other suitable cutting implements
that are adapted to cut or remove portions from the workpieces. The
particular form of cutting tool 14 will vary depending upon the
various embodiments of machine 10. For example, in table saws,
miter saws, circular saws and radial arm saws, cutting tool 14 will
typically include one or more circular rotating blades having a
plurality of teeth disposed along the perimetrical edge of the
blade. For a jointer or planer, the cutting tool typically includes
a plurality of radially spaced-apart blades. For a band saw, the
cutting tool includes an elongate, circuitous tooth-edged band.
[0015] Safety system 18 includes a detection subsystem 22, a
reaction subsystem 24 and a control subsystem 26. Control subsystem
26 may be adapted to receive inputs from a variety of sources
including detection subsystem 22, reaction subsystem 24, operative
structure 12 and motor assembly 16. The control subsystem may also
include one or more sensors adapted to monitor selected parameters
of machine 10. In addition, control subsystem 26 typically includes
one or more instruments operable by a user to control the machine.
The control subsystem is configured to control machine 10 in
response to the inputs it receives.
[0016] Detection subsystem 22 is configured to detect one or more
dangerous, or triggering, conditions during use of machine 10. For
example, the detection subsystem may be configured to detect that a
portion of the user's body is dangerously close to, or in contact
with, a portion of cutting tool 14. As another example, the
detection subsystem may be configured to detect the rapid movement
of a workpiece due to kickback by the cutting tool, such as is
described in U.S. Provisional Patent Application Serial No.
60/182,866, filed Feb. 16, 2000, and U.S. Pat. No. 4,267,914, the
disclosures of which are herein incorporated by reference. In some
embodiments, detection subsystem 22 may inform control subsystem 26
of the dangerous condition, which then activates reaction subsystem
24. In other embodiments, the detection subsystem may be adapted to
activate the reaction subsystem directly.
[0017] Once activated in response to a dangerous condition,
reaction subsystem 24 is configured to engage operative structure
12 quickly to prevent serious injury to the user. It will be
appreciated that the particular action to be taken by reaction
subsystem 24 will vary depending on the type of machine 10 and/or
the dangerous condition that is detected. For example, reaction
subsystem 24 may be configured to do one or more of the following:
stop the movement of cutting tool 14, disconnect motor assembly 16
from power source 20, place a barrier between the cutting tool and
the user, or retract the cutting tool from its operating position,
etc. The reaction subsystem may be configured to take a combination
of steps to protect the user from serious injury. Placement of a
barrier between the cutting tool and teeth is described in more
detail in U.S. Provisional Patent Application Serial No.
60/225,206, filed Aug. 14, 2000, entitled "Cutting Tool Safety
System," the disclosure of which is herein incorporated by
reference. Retraction of the cutting tool from its operating
position and/or the stopping of translational motion of the cutting
tool are described in more detail in the following U.S. Provisional
Patent Applications, all the disclosures of which are herein
incorporated by reference: Serial No. 60/225,089, filed Aug. 14,
2000, entitled "Retraction System For Use In Power Equipment,"
Serial No. 60/270,941, filed Feb. 22, 2001, entitled "Power Saw
with Improved Safety System," Serial No. 60/270,942, filed Feb. 22,
2001, entitled "Miter Saw with Improved Safety System," Serial No.
60/273,177, filed Mar. 2, 2001, entitled "Table Saw With Improved
Safety System," Serial No. 60/273,178, filed Mar. 2, 2001, entitled
"Miter Saw with Improved Safety System," Serial No. 60/273,902,
filed Mar. 6, 2001, entitled "Miter Saw with Improved Safety
System," Serial No. 60/275,594, filed Mar. 13, 2001, entitled
"Miter Saw with Improved Safety System," Serial No. 60/275,595,
filed Mar. 13, 2001, entitled "Safety Systems for Power Equipment,"
Serial No. 60/279,313, filed Mar. 27, 2001, entitled "Miter Saw
with Improved Safety System," and Serial No. 60/292,081, filed May
17, 2001, entitled "Translation Stop for Use in Power
Equipment."
[0018] The configuration of reaction subsystem 24 typically will
vary depending on which action(s) are taken. In the exemplary
embodiment depicted in FIG. 1, reaction subsystem 24 is configured
to stop the movement of cutting tool 14 and includes a brake
mechanism 28, a biasing mechanism 30, a restraining mechanism 32,
and a release mechanism 34. Brake mechanism 28 is adapted to engage
operative structure 12 under the urging of biasing mechanism 30.
During normal operation of machine 10, restraining mechanism 32
holds the brake mechanism out of engagement with the operative
structure. However, upon receipt of an activation signal by
reaction subsystem 24, the brake mechanism is released from the
restraining mechanism by release mechanism 34, whereupon, the brake
mechanism quickly engages at least a portion of the operative
structure to bring the cutting tool to a stop.
[0019] It will be appreciated by those of skill in the art that the
exemplary embodiment depicted in FIG. 1 and described above may be
implemented in a variety of ways depending on the type and
configuration of operative structure 12. Turning attention to FIG.
2, one example of the many possible implementations of safety
system 18 is shown. System 18 is configured to engage an operative
structure having a cutting tool in the form of a circular blade 40
mounted on a rotating shaft or arbor 42. Blade 40 includes a
plurality of cutting teeth (not shown) disposed around the outer
edge of the blade. As described in more detail below, braking
mechanism 28 is adapted to engage the teeth of blade 40 and stop
the rotation of the blade. U.S. Provisional Patent Application
Serial No. 60/225,210, filed Aug. 14, 2000, entitled "Translation
Stop For Use In Power Equipment," and U.S. Provisional Patent
Application Serial No. 60/233,459, filed Sep. 18, 2000, entitled
"Translation Stop For Use In Power Equipment," the disclosures of
which are herein incorporated by reference, describe other systems
for stopping the movement of the cutting tool. Although the
embodiment depicted in FIGS. 1 and 2 schematically illustrate
machine 10 as a generic woodworking machine, it will be appreciated
that safety system 18 may be incorporated into virtually any
specific type of woodworking machine. For example, the following
U.S. Provisional Patent Applications, the disclosures of which are
herein incorporated by reference, describe safety system 18 in the
context of various specific types of machines such as table saws,
miter saws, radial arm saws, band saws, pneumatic up-cut saws,
routers, etc.: U.S. Provisional Patent Application Serial No.
60/225,058, filed Aug. 14, 2000, entitled "Table Saw With Improved
Safety System," U.S. Provisional Patent Application Serial No.
60/225,057, filed Aug. 14, 2000, entitled "Miter Saw With Improved
Safety System," U.S. Provisional Patent Application Serial No.
60/233,459, filed Sep. 18, 2000, entitled "Translation Stop For Use
In Power Equipment," U.S. Provisional Patent Application Serial No.
60/270,941, filed Feb. 22, 2001, entitled "Power Saw With Improved
Safety System," U.S. Provisional Patent Application Serial No.
60/270,942, filed Feb. 22, 2001, entitled "Miter Saw With Improved
Safety System," U.S. Provisional Patent Application Serial No.
60/273,177, filed Mar. 2, 2001, entitled "Table Saw With Improved
Safety System," U.S. Provisional Patent Application Serial No.
60/273,178, filed Mar. 2, 2001, entitled "Miter Saw With Improved
Safety System," U.S. Provisional Patent Application Serial No.
60/273,902, filed Mar. 6, 2001, entitled "Miter Saw With Improved
Safety System," U.S. Provisional Patent Application Serial No.
60/275,594, filed Mar. 13, 2001, entitled "Miter Saw With Improved
Safety System," U.S. Provisional Patent Application Serial No.
60/275,595, filed Mar. 13, 2001, entitled "Safety Systems For Power
Equipment," U.S. Provisional Patent Application Serial No.
60/279,313, filed Mar. 27, 2001, entitled "Miter Saw With Improved
Safety System," U.S. Provisional Patent Application Serial No.
60/292,081, filed May 17, 2001, entitled "Translation Stop For Use
In Power Equipment," U.S. Provisional Patent Application Serial No.
60/292,100, filed May 17, 2001, entitled "Band Saw with Improved
Safety System," U.S. Provisional Patent Application Serial No.
60/298,207, filed Jun. 13, 2001, entitled "Apparatus And Method For
Detecting Dangerous Conditions In Power Equipment," and U.S.
Provisional Patent Application Serial No. 60/306,202, filed Jul.
18, 2001, entitled "Router With Improved Safety System."
[0020] In the exemplary implementation, detection subsystem 22 is
adapted to detect the dangerous condition of the user coming into
contact with blade 40. The detection subsystem includes a sensor
assembly, such as contact detection plates 44 and 46, configured to
detect any contact between the user's body and the blade. The
detection subsystem is adapted to transmit a signal to control
subsystem 26 when contact between the user and the blade is
detected. Various exemplary embodiments and implementations of
detection subsystem 22 are described in more detail in U.S.
Provisional Patent Application Serial No. 60/225,200, filed Aug.
14, 2000, entitled "Contact Detection System For Power Equipment,"
U.S. Provisional Patent Application Serial No. 60/225,211, filed
Aug. 14, 2000, entitled "Apparatus And Method For Detecting
Dangerous Conditions In Power Equipment," U.S. Provisional Patent
Application Serial No. 60/270,011, filed Feb. 20, 2001, entitled
"Contact Detection System for Power Equipment," U.S. Provisional
Patent Application Serial No. 60/292,100, filed May 17, 2001,
entitled "Band Saw With Improved Safety System," U.S. Provisional
Patent Application Serial No. 60/298,207, filed Jun. 13, 2001,
entitled "Apparatus And Method For Detecting Dangerous Conditions
In Power Equipment," and U.S. Provisional Patent Application Serial
No. 60/302,937, filed Jul. 2, 2001, entitled "Discrete Proximity
Detection System," the disclosures of which are herein incorporated
by reference.
[0021] Control subsystem 26 includes one or more instruments 48
that are operable by a user to control the motion of blade 40.
Instruments 48 may include start/stop switches, speed controls,
direction controls, etc. Control subsystem 26 also includes a logic
controller 50 connected to receive the user's inputs via
instruments 48. Logic controller 50 is also connected to receive a
contact detection signal from detection subsystem 22. Further, the
logic controller may be configured to receive inputs from other
sources (not shown) such as blade motion sensors, workpiece
sensors, etc. In any event, the logic controller is configured to
control operative structure 12 in response to the user's inputs
through instruments 48. However, upon receipt of a contact
detection signal from detection subsystem 22, the logic controller
overrides the control inputs from the user and activates reaction
subsystem 24 to stop the motion of the blade. Various exemplary
embodiments and implementations of control subsystem 26 are
described in more detail in U.S. Provisional Patent Application
Serial No. 60/225,059, filed Aug. 14, 2000, entitled "Logic Control
For Fast Acting Safety System," and U.S. Provisional Patent
Application Serial No. 60/225,094, filed Aug. 14, 2000, entitled
"Motion Detecting System For Use In Safety System For Power
Equipment," the disclosures of which are herein incorporated by
reference.
[0022] In the exemplary implementation, brake mechanism 28 includes
a pawl 60 mounted adjacent the edge of blade 40 and selectively
moveable to engage and grip the teeth of the blade. Pawl 60 may be
constructed of any suitable material adapted to engage and stop the
blade. As one example, the pawl may be constructed of a relatively
high strength thermoplastic material such as polycarbonate,
ultrahigh molecular weight polyethylene (UHMW) or Acrylonitrile
Butadiene Styrene (ABS), etc., or a metal such as aluminum, etc. It
will be appreciated that the construction of pawl 60 will vary
depending on the configuration of blade 40. In any event, the pawl
is urged into the blade by a biasing mechanism in the form of a
spring 66. In the illustrative embodiment shown in FIG. 2, pawl 60
is pivoted into the teeth of blade 40. It should be understood that
sliding or rotary movement of pawl 60 may also be used. The spring
is adapted to urge pawl 60 into the teeth of the blade with
sufficient force to grip the blade and quickly bring it to a
stop.
[0023] The pawl is held away from the edge of the blade by a
restraining mechanism in the form of a fusible member 70. The
fusible member is constructed of a suitable material adapted to
restrain the pawl against the bias of spring 66, and also adapted
to melt under a determined electrical current density. Examples of
suitable materials for fusible member 70 include NiChrome wire,
stainless steel wire, etc. The fusible member is connected between
the pawl and a contact mount 72. Preferably member 70 holds the
pawl relatively close to the edge of the blade to reduce the
distance the pawl must travel to engage the blade. Positioning the
pawl relatively close to the edge of the blade reduces the time
required for the pawl to engage and stop the blade. Typically, the
pawl is held approximately {fraction (1/32)}-inch to 1/4-inch from
the edge of the blade by fusible member 70, however other
pawl-to-blade spacings may also be used within the scope of the
invention.
[0024] Pawl 60 is released from its unactuated, or cocked, position
to engage blade 40 by a release mechanism in the form of a firing
subsystem 76. The firing subsystem is coupled to contact mount 72,
and is configured to melt fusible member 70 by passing a surge of
electrical current through the fusible member. Firing subsystem 76
is coupled to logic controller 50 and activated by a signal from
the logic controller. When the logic controller receives a contact
detection signal from detection subsystem 22, the logic controller
sends an activation signal to firing subsystem 76, which melts
fusible member 70, thereby releasing the pawl to stop the blade.
Various exemplary embodiments and implementations of reaction
subsystem 24 are described in more detail in U.S. Provisional
Patent Application Serial No. 60/225,056, filed Aug. 14, 2000,
entitled "Firing Subsystem For Use In Fast Acting Safety System,"
U.S. Provisional Patent Application Serial No. 60/225,170, filed
Aug. 14, 2000, entitled "Spring-Biased Brake Mechanism for Power
Equipment," and U.S. Provisional Patent Application Serial No.
60/225,169, filed Aug. 14, 2000, entitled "Brake Mechanism For
Power Equipment," U.S. Provisional Patent Application Serial No.
60/279,313, filed Mar. 27, 2001, entitled "Miter Saw With Improved
Safety System," U.S. Provisional Patent Application Serial No.
60/292,081, filed May 17, 2001, entitled "Translation Stop For Use
In Power Equipment," U.S. Provisional Patent Application Serial No.
60/292,100, filed May 17, 2001, entitled "Band Saw With Improved
Safety System," U.S. Provisional Patent Application Serial No.
60/302,916, filed Jul. 3, 2001, entitled "Actuators For Use With
Fast-Acting Safety Systems," and U.S. Provisional Patent
Application Serial No. 60/307,756, filed Jul. 25, 2001, entitled
"Actuators For Use With Fast-Acting Safety Systems," the
disclosures of which are herein incorporated by reference.
[0025] It will be appreciated that activation of the brake
mechanism will require the replacement of one or more portions of
safety system 18. For example, pawl 60 and fusible member 70
typically must be replaced before the safety system is ready to be
used again. Thus, it may be desirable to construct one or more
portions of safety system 18 in a cartridge that can be easily
replaced. For example, in the exemplary implementation depicted in
FIG. 2, safety system 18 includes a replaceable cartridge 80 having
a housing 82. Pawl 60, spring 66, fusible member 70 and contact
mount 72 are all mounted within housing 82. Alternatively, other
portions of safety system 18 may be mounted within the housing. In
any event, after the reaction system has been activated, the safety
system can be reset by replacing cartridge 80. The portions of
safety system 18 not mounted within the cartridge may be replaced
separately or reused as appropriate. Various exemplary embodiments
and implementations of a safety system using a replaceable
cartridge are described in more detail in U.S. Provisional Patent
Application Serial No. 60/225,201, filed Aug. 14, 2000, entitled
"Replaceable Brake Mechanism For Power Equipment," U.S. Provisional
Patent Application Serial No. 60/225,212, filed Aug. 14, 2000,
entitled "Brake Positioning System," U.S. Provisional Patent
Application Serial No. 60/279,313, filed Mar. 27, 2001, entitled
"Miter Saw With Improved Safety System," U.S. Provisional Patent
Application Serial No. 60/306,202, filed Jul. 18, 2001, entitled
"Router With Improved Safety System," U.S. Provisional Patent
Application Serial No. 60/302,916, filed Jul. 3, 2001, entitled
"Actuators For Use With Fast-Acting Safety Systems," and U.S.
Provisional Patent Application Serial No. 60/307,756, filed Jul.
25, 2001, entitled "Actuators For Use With Fast-Acting Safety
Systems," the disclosures of which are herein incorporated by
reference.
[0026] Additional variations and modifications of safety system 18
are described in U.S. Provisional Patent Application Serial No.
60/182,866, filed Feb. 16, 2000, and No. 60/157,340, filed Oct. 1,
1999, both entitled "Fast-Acting Safety Stop," the disclosures of
which are herein incorporated by reference.
[0027] It is believed that the disclosure set forth above
encompasses multiple distinct inventions with independent utility.
While each of these inventions has been disclosed in its preferred
form, the specific embodiments thereof as disclosed and illustrated
herein are not to be considered in a limiting sense as numerous
variations are possible. The subject matter of the inventions
includes all novel and non-obvious combinations and
sub-combinations of the various elements, features, functions
and/or properties disclosed herein. No single feature, function,
element or property of the disclosed embodiments is essential to
all of the disclosed inventions. Similarly, where the claims recite
"a" or "a first" element or the equivalent thereof, such claims
should be understood to include incorporation of one or more such
elements, neither requiring nor excluding two or more such
elements.
[0028] It is believed that the following claims particularly point
out certain combinations and sub-combinations that are directed to
one of the disclosed inventions and are novel and non-obvious.
Inventions embodied in other combinations and sub-combinations of
features, functions, elements and/or properties may be claimed
through amendment of the present claims or presentation of new
claims in this or a related application. Such amended or new
claims, whether they are directed to a different invention or
directed to the same invention, whether different, broader,
narrower or equal in scope to the original claims, are also
regarded as included within the subject matter of the inventions of
the present disclosure.
* * * * *